JEE Main 2015 · 10 Apr · Shift 1 · Chemistry Q39

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ChemistrySingle correct+4 / -1Question 39 of 90

The reaction
$\ce{2N2O5(g) -> 4NO2(g) + O2(g)}$
follows first order kinetics. The pressure of a vessel containing only $\ce{N2O5}$ was found to increase from 50 mm Hg to 87.5 mm Hg in 30 min. The pressure exerted by the gases after 60 min. will be (Assume temperature remains constant) :

106.25 mm Hg

116.25 mm Hg

125 mm Hg

150 mm Hg

Answer and worked solution

Official answer: A

If $p$ is the drop in $\ce{N2O5}$ pressure, the total is $50+\frac32p$ . At 30 min this is 87.5, so $p=25$ : one half-life is 30 min.

At 60 min, $p=37.5$ , and the total is $50+56.25=106.25$ mm Hg.

Topics:Integrated rate equations Half-life

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JEE Main 2015 · 10 Apr · Shift 1, Chemistry question 39